The hepatic parenchymal cell surface membrane demonstrates structural and functional polarity, rapid and asynchronous turnover and adaptability to both endogenous and exogenous agents. Since bile flow is postulated to be controlled by the active excretion of bile acids and sodium, we identified the putative receptors for these substances and investigated the effect of bile secretory failure and pharmacological agents on their activity. We have demonstrated that cholestasis, phenobarbital and hormones differently alter the synthesis of liver surface membranes. The present studies are directed at the effect of these agents on membrane glycoproteins and the determination of the turnover of the specific liver surface membrane proteins (Na-K) ATPase and alkaline phosphatase. In addition, the physiological effects of altered (Na-K) ATPase activity on hepatic cell function will be determined. BIBLIOGRAPHIC REFERENCES: Vial, MacKinnon and Simon; Effect of cholestasis on the ultrastructural morphology of hepatocytes. Gastroent 70:85, 1976. Accatino and Simon; Identification and characterization of a bile acid receptor in isolated liver surface membranes. J. Clin. Invest. 57;496, 1976.